Syntheses and characterization of model imide compounds and chemical imidization study

Abstract

In order to characterize various depolymerization and imidization reactions involved during thermal and chemical imidazation of poly(amic acid) by UV-visible and fluorescence spectroscopies, several model compounds have been synthesized and characterized from 1,5-diaminonaphthalene (DAN) and phthalic anhydride. The model compounds synthesized are the derivatives of DAN such as amic acid-amine, diamic acid, amine-imide, amic acid-imide, diimide, and diisoimide. Only DAN is found to be strongly fluorescent while amic acid-amine, amine-imide, and diisoimide are very weakly fluorescent. The others have negligible fluorescence. During imidization, therefore, the fluorescence intensity can be used to quantify the amount of depolymerized DAN. Due to strong substituent effects on the UV-visible spectra, the model compounds exhibit characteristic absorption maxima and extinction coefficients. Proton NMR, IR, and differential scanning calorimetry have been used also to confirm the chémical structures and the purity of the model compounds. Chemical imidization using acetic anhydride and pyridine for polyamic acid made from DAN and a partially fluorinated dianhydride has been investigated. Deconvolution of UV-visible spectra on the basis of the model compounds provided the composition of the involved species such as diamic acid, diimide, and diisoimide. The rate constants for chemical imidization occurring in 1% solution in Nmethyl-2-pyrrolidinone indicate a fast first step in which simultaneous conversion of diamic acid to diimide and diisoimide takes place, followed by slower conversion of diisoimide to diimide in a second step.

Absorption, Fluorescence, and Thermal Properties of Transparent Polyimides Based on Cyclobutanetetracarboxylic Dianhydride

“…Comparing to the absorption spectra of PI(CBDA/DPM) in Figure 2a, PAA(CBDA/DPM) shows an absorption peak at 260 nm, while PI(CBDA/DPM) shows an absorption peak at 236 nm, which means a blue shift of 24 nm when the poly(amide acid) is imidized to the polyimide. Sung et al 30 studied the UV spectra of a model imide derived from 1 ,5-diaminonaphthalene (DAN) and phthalic anhydride, and found a blue shift of spectra when the amide acid was converted to an imide. In the present study, we used an alicyclic dianhydride, CBDA, which has no absorption in UV-Vis region.…”

13C NMR spectral assignment ofN-arylphthalisoimides

“…60 mg) were freshly dissolved in (1 ml) except compound 2. Owing to the isomerization CDCl 3 of N-(4-nitrophenyl)phthalisoimide (2) to N-(4-nitrophenyl)phthalimide occurring in their spectra were recorded in The CDCl 3 CD 2 Cl 2 . deuterium resonance of the solvent was used as an internal lock and tetramethylsilane was used as an internal reference for all spectra.…”

Fabrication of highly refractive barium‐titanate‐incorporated polyimide nanocomposite films with high permittivity and thermal stability

“…Then, phthalic anhydride (PA) and pyridine were added to the APS‐modified BT nanoparticle suspension and reacted for 15 h at ambient temperature. In this surface modification, which is expected to produce an N ‐( n ‐propyl)phthalimide (APS‐PI) bound to a silicon atom,, the molar amounts of PA and pyridine were four and three times as much as that of APS used above. Non‐reacted PA and pyridine in the suspension were removed by centrifuging and redispersion.…”